Global patterns of phosphatase activity in natural soils

Margalef O., Sardans J., Fernández-Martínez M., Molowny-Horas R., Janssens I.A., Ciais P., Goll D., Richter A., Obersteiner M., Asensio D., Peñuelas J. (2017) Global patterns of phosphatase activity in natural soils. Scientific Reports. 7: 0-0.
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Doi: 10.1038/s41598-017-01418-8

Resum:

Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity. © 2017 The Author(s).

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Els COVs al Montseny: entre l'smog urbà i la biogeneració.

Seco R, Peñuelas J, Filella I, Llusià J, Molowny-Horas R (2012). Els COVs al Montseny: entre l'smog urbà i la biogeneració. UABdivulga 03/2012.

Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: The effect of local biogenic emissions

Seco R., Peñuelas J., Filella I., Llusià J., Molowny-Horas R., Schallhart S., Metzger A., Müller M., Hansel A. (2011) Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: The effect of local biogenic emissions. Atmospheric Chemistry and Physics. 11: 13161-13179.
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Doi: 10.5194/acp-11-13161-2011

Resum:

Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce. We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a.s.l.) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air. The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NO x and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic VOCs emitted in the local valley by the vegetation, thus enhancing O 3 formation in this forested site. The only VOC species that showed a somewhat different daily pattern were monoterpenes because of their local biogenic emission. Isoprene also followed in part the daily pattern of monoterpenes, but only in summer when its biotic sources were stronger. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources. © 2011 Author(s).

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Analysis of decadal time series in wet N concentrations at five rural sites in NE Spain

Avila A., Molowny-Horas R., Gimeno B.S., Peñuelas J. (2010) Analysis of decadal time series in wet N concentrations at five rural sites in NE Spain. Water, Air, and Soil Pollution. 207: 123-138.
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Doi: 10.1007/s11270-009-0124-7

Resum:

Nitrogen emissions have grown in Spain during the last 15 years. As precipitation scavenges gases and aerosols from the atmosphere, an effect on rainwater concentrations can be expected. However, time-series studies on wet N concentrations in the Iberian Peninsula are very scarce. This paper aims to fill this gap by analysing weekly rainfall N concentrations at a set of rural sites in Catalonia (NE Spain) from 1995/1996 to 2007 and a forest site monitored from 1983 to 2007. The sites encompass a range of rural environments and climate conditions, from the inland pre-Pyrenees (Sort) to the Mediterranean coast (Begur) and from north (Sort and Begur) to central (Palautordera and La Castanya) and south Catalonia (La Senia). We found a 1-year cycle for concentrations of NH 4 + and NO 3 - whereby higher values were reached at the end of spring-early summer, except at the easternmost coastal site of Begur. Weekly NH 4 + concentrations decreased with time at all sites (except at La Senia) whilst NO 3 - concentrations increased at all sites during the same period. Rainfall SO 4 2- concentrations decreased with time at all sites. The opposite trends in NO 3 - and SO 4 2- concentrations determined a shift in the relative acid contribution of those anions during the 12-13-year period. To interpret the increasing trend, mean annual NO 3 - concentrations were regressed against NO 2 Spanish emissions and to some indicators of local anthropogenic activity. The increase at Sort and Palautordera showed good correlation with local anthropogenic indicators. Wet inorganic N deposition ranged between 4.2 and 6.7 kg ha -1 year -1. When including estimates of dry deposition, total annual deposition rose up to 10-20 kg ha -1 year -1, values that have been found to initiate adverse effects on Mediterranean-type forest ecosystems. © 2009 Springer Science+Business Media B.V.

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